title: Development of a comorbidity index for use in obstetric patients.
abstract: OBJECTIVE
  To develop and validate a maternal comorbidity index to predict severe maternal morbidity, defined as the occurrence of acute maternal end-organ injury, or mortality.
  
  
  METHODS
  Data were derived from the Medicaid Analytic eXtract for the years 2000-2007. The primary outcome was defined as the occurrence of maternal end-organ injury or death during the delivery hospitalization through 30 days postpartum. The data set was randomly divided into a two-thirds development cohort and a one-third validation cohort. Using the development cohort, a logistic regression model predicting the primary outcome was created using a stepwise selection algorithm that included 24-candidate comorbid conditions and maternal age. Each of the conditions included in the final model was assigned a weight based on its beta coefficient, and these were used to calculate a maternal comorbidity index.
  
  
  RESULTS
  The cohort included 854,823 completed pregnancies, of which 9,901 (1.2%) were complicated by the primary study outcome. The derived score included 20 maternal conditions and maternal age. For each point increase in the score, the odds ratio for the primary outcome was 1.37 (95% confidence interval [CI] 1.35-1.39). The c-statistic for this model was 0.657 (95% CI 0.647-0.666). The derived score performed significantly better than available comorbidity indices in predicting maternal morbidity and mortality.
  
  
  CONCLUSIONS
  This new maternal comorbidity index provides a simple measure for summarizing the burden of maternal illness for use in the conduct of epidemiologic, health services, and comparative effectiveness research.
  
  
  METHODS
  II.
authors.affiliation: Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, the Department of Anesthesiology, Critical Care, and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, and the Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts; the Department of Anesthesiology, University of Michigan Health System, Ann Arbor, Michigan; and the Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Bateman
authors.forename: Jill M
authors.initials: JM
authors.lastname: Mhyre
authors.forename: Sonia
authors.initials: S
authors.lastname: Hernandez-Diaz
authors.forename: Krista F
authors.initials: KF
authors.lastname: Huybrechts
authors.forename: Michael A
authors.initials: MA
authors.lastname: Fischer
authors.forename: Andreea A
authors.initials: AA
authors.lastname: Creanga
authors.forename: William M
authors.initials: WM
authors.lastname: Callaghan
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Gagne
mesh_terms: D000208:Acute Disease / Q000401:mortality; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D015897:Comorbidity; D036861:Delivery, Obstetric / Q000401:mortality*; D004211:Disseminated Intravascular Coagulation / Q000401:mortality; D005260:Female; D006333:Heart Failure / Q000401:mortality; D006801:Humans; D016015:Logistic Models; D008484:Medicaid / Q000706:statistics & numerical data; D008875:Middle Aged; D049590:Postpartum Period; D011247:Pregnancy; D011248:Pregnancy Complications / Q000401:mortality*; D015203:Reproducibility of Results; D018570:Risk Assessment; D018805:Sepsis / Q000401:mortality; D012720:Severity of Illness Index; D014481:United States; D055815:Young Adult